Novel additives for imparting Mar and scratch resistance and compositions comprising the same

ABSTRACT

Additives comprising dispersed silica nanoparticles are disclosed. The silica nanoparticles are dispersed in an aminoplast, such as a modified aminoplast formed from the reaction between an aminoplast, a modifying component, and optionally a siloxane. The resulting additives can be added to coating compositions to provide improved mar and/or scratch resistance.

FIELD OF THE INVENTION

The present invention relates to novel additives for coatingcompositions that provide improved mar and/or scratch resistance to thecured coating. More specifically, the improved resistance is achieved byincorporating the additives into a film-forming resin.

BACKGROUND OF THE INVENTION

“Color-plus-clear” coating systems involving the application of acolored or pigmented basecoat to a substrate followed by application ofa transparent or clearcoat over the basecoat have become increasinglypopular as original finishes for a number of consumer productsincluding, for example, cars and floor coverings such as ceramic tilesand wood flooring. The color-plus-clear coating systems have outstandingappearance properties such as gloss and distinctness of image, due inlarge part to the clear coat.

“One coat” systems comprising a one coat color layer are appliedthemselves as the topcoat. One coat systems are frequently used forhousehold appliances, lawn and garden equipment, interior fixtures, andthe like.

Many of the coatings used in both the color-plus-clear systems andone-coat systems are powder coatings. In recent years, powder coatingshave become increasingly popular because these coatings are inherentlylow in volatile organic content (VOC). The low VOC significantly reducesair emissions during application and curing as compared to liquidcoatings. Liquid coatings are still used in many systems, however,particularly those wherein solvent emissions are permitted. For example,the coating of elastomeric automotive parts is often done by sprayingliquid compositions.

Topcoat film-forming compositions, such as the protective and/ordecorative one coats for household appliances and the transparentclearcoat in color-plus-clear coating systems for automotiveapplications, are subject to defects that occur during the assemblyprocess and damage from both the environment and normal use of the endproduct. Paint defects that occur during assembly include the paintlayer being too thick or too thin, “fish eyes” or craters, andunder-cured or over-cured paint; these defects can affect the color,brittleness, solvent resistance and mar and scratch performance of thecoating. Damaging environmental factors include acidic precipitation,exposure to ultraviolet radiation from sunlight, high relative humidityand high temperatures; these factors can also result in compromisedperformance. Normal use of consumer products will often lead to marring,scratching and/or chipping of the surface due to contact with hardobjects, contact with brushes and/or abrasive cleansers during normalcleaning processes, and the like.

Thus, there is a need in the coatings art for topcoats having goodscratch and mar resistance.

SUMMARY OF THE INVENTION

The present invention is directed to an additive for use in coatingcompositions, including both liquid and powder coating compositions. Theadditive itself can be in either liquid or powder form, and generallycomprises aminoplast compounds and silica nanoparticles; thenanoparticulate silica is dispersed throughout the aminoplast. Coatingcompositions comprising these additives and methods for using thesecompositions are also within the scope of the invention, as are articlescoated according to these methods.

Historically, incorporation of silica nanoparticles into coatings,especially powder coatings, has been very hard to achieve, as the silicaparticles tend to form agglomerates when mixed into the coating. Theseagglomerates are relatively ineffective in imparting mar and/or scratchresistance to a coating, and can also negatively affect the appearanceof the coating. It has now been surprisingly discovered that silicananoparticles can be introduced to a coating composition through anaminoplast dispersant; the aminoplast dispersant minimizes, if notprevents, the agglomeration of the silica, thereby allowing it to bedispersed both throughout the aminoplast itself and the coatingcomposition. Incorporation of the present additives into compositionscomprising film-forming resins results in coatings having enhanced marand/or scratch resistance as compared with the same coatings lackingthese additives. According to the present invention, coatings can beformulated with these improved mar and/or scratch characteristicswithout significantly affecting the appearance or other mechanicalproperties of the coatings.

“Mar” and “scratch” refer herein to physical deformations resulting frommechanical or chemical abrasion. “Mar resistance” is a measure of amaterial's ability to resist appearance degradation caused by smallscale mechanical stress. “Scratch resistance” is the ability of amaterial to resist more severe damage that can lead to visible, deeperor wider trenches. Thus, scratches are generally regarded as being moresevere than what is referred to in the art as mar, and the two areregarded in the art as being different. As noted above, marring andscratching can result from manufacturing and environmental factors aswell as through normal use. Although mar and scratch are in manyrespects differing degrees of the same thing, a coating that improvesmar resistance may not be effective in improving scratch resistance, andvice versa. It will be appreciated, therefore, that the presentadditives can be used in conjunction with other additives that impartimproved mar and/or scratch resistance to coatings.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed to an additive comprising anaminoplast and silica nanoparticles, sometimes referred to herein as the“present additive”. Particularly suitable aminoplasts are “modifiedaminoplasts” formed from the reaction between an aminoplast and one ormore modifying components, as further described below. The additives aregenerally prepared by mixing together one or more aminoplasts withsilica nanoparticles, which will be understood as being dispersed inorganic solvent. The aminoplast is used in an amount sufficient todisperse the silica in the resulting mixture.

Any aminoplast known in the art can be used according to the presentinvention, in either an unmodified form or modified as discussed below.As will be known to those in the art, aminoplast resins are based on thecondensation products of an amino- or amido-group containing compoundwith an aldehyde, such as formaldehyde, acetaldehyde, crotonaldehyde,acrolein, benzaldehyde, furfural and glyoxal; formaldehyde is most oftenused. The reaction product of an amino- or amido group-containingcompound and an aldehyde is often reacted further with an alcohol toproduce partially or fully alkylated derivatives. These derivatives arealso “aminoplasts” within the present invention.

The term “aminoplast” also includes phenoplasts (phenolic resins),specifically, the resole-type resins that are the reaction product ofphenol and an aldehyde, and that have the further property of containingpendant hydroxymethyl or alkoxymethyl groups. Resole resins andresolated novolac resins are examples of suitable phenoplasts.

Dimeric and oligomeric products resulting from self-condensationreactions that occur during aminoplast formation are also “aminoplasts”within the present invention.

The aminoplasts used in the present invention can be generallyrepresented by the formula:A-(R)_(n)wherein the “A” group in A-(R)_(n) is an n-functional polyamino anchormolecule connected to (R)_(n) groups via the nitrogens. Suitable “A”groups include glycoluril ureas, melamine, guanamine, and the like. The“R” group in A-(R)_(n) can be hydrogen, an alkyl group of 1 to 10 carbonatoms, a crosslinkable group such as —CH₂OH or —CH₂OR⁸ wherein R⁸ is analkyl group of 1 to 10 carbon atoms, or an aminoplast group-containingoligomeric group provided that the total number of the crosslinkablegroups per each aminoplast crosslinking agent is at least 2. The “n” inA-(R)_(n) is the total functionality of the polyamino anchor molecule A,and is 2 or greater. Suitable aminoplasts are further described in U.S.Pat. No. 5,256,493, hereby incorporated by reference.

The aminoplasts used according to the present invention can be eitherliquid or solid at room temperature (i.e. 20° C.). Examples of suitableliquid aminoplasts include those in the CYMEL line, commerciallyavailable from Cytec Industries, Inc., and those in the RESIMENE line,commercially available from Solutia, Inc. Most of these products arealkyl ethers derived from hexamethylol melamine. An example of asuitable solid aminoplast is POWDERLINK 1174, a methyl ether derivativeof tetramethylol glycoluril, also commercially available from CytecIndustries Inc.

In addition to using commercially available aminoplasts, modifiedversions of these aminoplasts can also be used. This is especially truefor powder coating applications where solid aminoplast crosslinkers arenot widely available. Certain aminoplasts are better suited formodification than others. A particularly suitable aminoplast, or “A” inthe formula above, for use in forming a modified aminoplast is anaminotriazine compound having one or less nonalkylated NH bond pertriazine ring; this can include aminoplast resins such as alkoxyalkylaminotriazine compounds, for example, derivatives of melamine,benzoguanamine, acetoguanamine, formoguanamine, spiroguanamine and thelike. Aminoplast resins for use as the aminotriazine compound include,for example, highly alkylated, low imino aminoplast resins.(Methoxymethyl)aminotriazine compounds are particularly suitable. Suchcompounds are commercially available from Solutia, Inc. as RESIMENECE-7103, 745, and 747 and from Cytec Industries, Inc. as CYMEL 300, 303,1116, 1123, 1133, 1135, 1156, and 1168.

In another embodiment wherein a modified aminoplast is formed, “A” is analkoxylated aldehyde condensate of glycoluril. Such compounds can beprepared, for example, by reacting glycoluril, or acetylene diurea, withan aldehyde, such as formaldehyde, to form tetra-alkylol glycoluril. Inone embodiment, the alkylol groups are etherified with a mono-alcohol,such as a C₁ to C₆ mono-alcohol, to form tetra-alkoxy alkyl glycoluril.An example of such a tetra-alkoxyalkyl glycoluril is tetra-methoxymethyl glycoluril, commercially available as POWDERLINK 1174 from CytecIndustries, Inc. Also suitable is cyclohexanol etherified tetra-methylolglycoluril.

In one embodiment of the present invention, the aminoplast resinscomprise highly alkylated, low imino aminoplast resins that have adegree of polymerization (“DP”) of less than 2.0, often less than 1.8,and typically less than 1.5. Generally, the number average degree ofpolymerization is defined as the average number of structural units perpolymer chain. For purposes of the present invention, a DP of 1.0 wouldindicate a completely monomeric triazine structure, while a DP of 2.0indicates two triazine rings joined by a methylene or methylene-oxybridge. It should be understood that the DP values reported hereinrepresent average DP values as determined by gel permeationchromatography data. It should be further understood that not everyaminoplast can be modified by every one of the modifying componentsdiscussed herein. For example, if the modifying component ispolyfunctional and reacts with the aminoplast more than once, low DP(i.e. <1.8) aminoplasts should be used. If the modifying component ismonofunctional or behaves like a monofunctional compound (such as amonohydroxy phenol), there is no restriction on the DP value of theaminoplast.

Modification of the aminoplast is effected by reacting an aminoplastresin with a modifying component. If the starting aminoplast resin isliquid, the modifying component is one that, upon reaction with theaminoplast, will result in a solid or ungelled product; in this case,the modifying component can be more specifically described as a powderforming component. If the starting aminoplast resin is already solid,the modifying component is one that, upon reaction with the aminoplast,will result in a solid or ungelled product that either will not lowerthe glass transition temperature (“Tg”) of a coating composition towhich it is added or that will lower the amount of gassing during curingof a coating composition as compared to the unmodified aminoplast.

To determine whether a compound is a modifying component (also referredto herein as a modifying compound) within the present invention, areaction with an aminoplast can be run as described below. If the resultof the reaction is to convert a liquid aminoplast to a solid or ungelledreaction product, the compound is a modifying compound; if the result ofthe reaction is to improve the performance characteristics of a solidaminoplast as described above, the compound is also a modifying compoundwithin the present invention. Some modifying components will have two ormore reactive groups. Examples of suitable modifying components includemonohydroxy phenol derivatives, polyhydric compounds, polyester polyolsand urethanes, such as those described below. Other compounds suitablefor use as modifying components are also discussed below. Combinationsof modifying components can be used according to the present invention.

The phenol derivatives can be, for example, monohydroxy aromaticcompounds having the following structure (I):

wherein R₁ through R₅ are the same or different and can be H; amonovalent hydrocarbon group; COOR₆; NO₂; halogen; or XR₇; where R₆ is Hor a monovalent hydrocarbon group, X is O or S, and R₇ is a monovalenthydrocarbon group having 1 to 8 carbon atoms. At least one of R₃ and R₄is H. When R₄ is H and R₃ is not, R₁ and R₂ taken together, R₁ and R₅taken together, or R₂ and R₃ taken together can be fused aliphatic oraromatic ring structures; when R₃ is H and R₄ is not, R₁ and R₂ takentogether, R₁ and R₅ taken together, or R₅ and R₄ taken together can befused aliphatic or aromatic ring structures. Similarly, if R₃ and R₄ areboth H, R₁ and R₂ taken together or R₁ and R₅ taken together can befused aliphatic or aromatic ring structures. In a particularly suitableembodiment of the compound having Structure I, R₃ and R₄ are both H; inanother particularly suitable embodiment, R₁ is selected from aryl,alkylaryl, alkoxy, COOH, NO₂ and halogen. In another particularlysuitable embodiment, R₁ and either R₃ or R₄ are tertiary butyl groups.

By “monovalent hydrocarbon group” is meant an organic group containingcarbon and hydrogen. The hydrocarbon groups may be aliphatic oraromatic, and may contain from 1 to 24 (in the case of aromatic from 3to 24) carbon atoms. A “monovalent hydrocarbon group” can also be aheteroatomic hydrocarbon group, that is, one or more of the carbonmolecules in the groups can be substituted with heteroatoms, typicallyoxygen or nitrogen. Nonlimiting examples of such monovalent hydrocarbongroups include alkyl, alkoxyl, aryl, alkylaryl or alkoxyaryl groups.

By “alkyl” is meant acyclic or cyclic groups having a carbon chainlength of from C₁ to C₂₅. By “alkoxyl” is meant an alkyl groupcontaining at least one oxygen atom, such as an ether oxygen, and havinga carbon chain length of from C₂ to C₂₅, such as from C₂ to C₈; thisincludes compounds having one or more ester linkages. An “aryl” group isan aromatic group containing one or more aromatic rings, fused orunfused, containing 3 to 24 carbons. By “alkylaryl” is meant an acyclicalkyl group having a carbon chain length of from C₂ to C₂₅ andcontaining at least one aryl group, such as phenyl. Similarly,“alkoxyaryl” refers to an alkyl group containing at least one oxygenatom and having a carbon chain length of from C₂ to C₂₅, and at leastone aryl group. The aryl group(s), either alone or in conjunction withan alkyl or alkoxy group, may optionally be substituted. Suitablesubstituents include heteroatoms (O, N and S), hydroxyl, benzyl,carboxylic acid, alkoxy and alkyl groups, for example.

Nonlimiting examples of monohydroxy aromatic compounds suitable for useas the modifying component in the present invention include p-cresol,4-methoxyphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol,4-nitrophenol, 4-fluorophenol, 2-phenylphenol, 4-phenylphenol,1-napthol, and 2-naphthol. In one embodiment, the monohydroxy aromaticcompound comprises 4-tert-butylphenol.

Suitable polyhydric compounds useful as modifying components can be anyof a variety of compounds having two or more groups reactive towards theaminoplast. These polyhydric compounds can be aliphatic, cycloaliphaticor aromatic. For example, when the aminoplast is POWDERLINK 1174, thepolyhydric compound can contain hydroxyl groups. In one embodiment, thepolyhydric compound comprises a diol, a triol, or a mixture of the two.Examples of suitable diols include cycloaliphatic diols, such ashydrogenated Bisphenol A, cyclohexane dimethanol, cyclohexane diol andmixtures thereof. Cyclohexane dimethanol and hydrogenated Bisphenol Aare particularly suitable. Examples of suitable triols includetrimethylol propane, tris(hydroxyethyl) isocyanurate, and mixturesthereof.

The polyhydric aromatic compounds can be any of a variety of polyhydricaromatic compounds known in the art, such as dihydric aromaticcompounds. Suitable polyhydric aromatic compounds are generallyrepresented by the following structures (II) or (III):HO-Φ¹-Y-Φ²-OH   (II)orHO-Φ³-OH   (III)where Φ¹, Φ² and Φ³ are the same or different and each independentlyrepresents a divalent aromatic group; Y represents a polyvalent linkinggroup.

By “divalent aromatic group” is meant any divalent group derived from asubstituted or unsubstituted aromatic compound. Examples of suitablesubstituent groups include alkyl, alkoxy, aryl, alkylaryl groups,heteroatoms such as nitrogen or oxygen, and halogen atoms, for examplechlorine and bromine, provided that at least one of the positions orthoto each OH group is hydrogen substituted.

The polyvalent linking group Y can be any polyvalent atom or radical,for example oxygen, sulfur, —SO—, —SO₂—, divalent hydrocarbon radicalscontaining up to 10 carbon atoms, and sulfur-, silicon- ornitrogen-containing hydrocarbon radicals. In one embodiment, Y is adivalent C₃ hydrocarbon radical.

In certain embodiments of the invention, the polyhydric aromaticcompound is selected from 4,4′-isopropylidenediphenol (Bisphenol A),bis(4-hydroxyphenyl)methane, 2,2′-biphenol, dihydroxynaphthalene,resorcinol, hydroquinone, catechol and mixtures thereof. Bisphenol A isparticularly suitable.

The polyester polyols used as the modifying component in the presentinvention can comprise the polyester polyol condensation reactionproduct of (a) a cycloaliphatic polyol and (b) a cyclic polycarboxylicacid or anhydride.

The cycloaliphatic polyol can be any of a variety of polyhydriccycloaliphatic compounds known in the art. Suitable examples includehydrogenated Bisphenol A, hydrogenated Bisphenol F, hydrogenatedBisphenol E, M, P, Z, and the like, cyclohexyl dimethanol, cyclohexanediol and mixtures thereof. Hydrogenated Bisphenol A is especiallysuitable.

The cyclic polycarboxylic acid or anhydride can be any cyclic compoundhaving two or more carboxylic acid groups per molecule. For example, thecyclic polycarboxylic acid/anhydride can be hexahydrophthalic acid,phthalic acid, isophthalic acid, terephthalic acid, anhydrides thereof,and mixtures thereof. Hexahydrophthalic anhydride is especiallysuitable.

The polyester polyol can be prepared by general condensation reactiontechniques well known in the art, so long as the ratio of reactants (a)and (b) and reaction conditions are such that the resulting condensationreaction product comprises two or more reactive hydroxyl groups permolecule. For purposes of the present invention, the molar ratio of thecycloaliphatic polyol (a) to the cyclic polycarboxylic acid or anhydride(b) typically ranges from 1.0 to 2.5:1, such as from 1.5 to 2.2:1 orfrom 1.8 to 2.2:1.

The polyester polyol can be prepared generally as follows. Theacid/anhydride and alcohol(s) are reacted using condensation techniqueswell known to the art. The reaction is monitored by periodic samplingfor acid value and hydroxyl number measurements. The reaction isterminated when these measurements meet the desired values. Typically,the acid value of the polyester polyol is between 0.1 and 20, such asbetween 0.5 and 5, and the hydroxyl value is greater than 130 and rangesfrom 130 to 190, such as from 140 to 175.

The polyester polyol typically has a number average molecular weight(“Mn”) ranging from 400 to 2000, such as from 400 to 1500, or from 400to 1000. Further, the polyester polyol typically has a Tg of at least30° C., such as at least 35° C., or at least 40° C., and a glasstransition temperature less than 120° C., such as less than 110° C., orless than 100° C. The Tg of the polyester polyol can range between anycombination of these values inclusive of the recited values. The Tg ofthe polyol can be measured experimentally using methods known in theart, such as differential scanning calorimetry (rate of heating 10° C.per minute, Tg taken at the first inflection point). Unless otherwiseindicated, the stated Tg as used herein refers to the measured Tg.

When a polyhydric compound or a polyester polyol is used as themodifying compound, the aminoplast that is modified should be one havinga low DP, such as <1.8 or <1.5.

Two different types of reactive urethane group-containing compounds(“urethane compounds”) can also be used as the modifying component ofthe present invention. The first of these urethane compounds comprisesthe reaction product of (a) a polyester polyol, and (b) amonoisocyanate. The polyester polyol (a) can be any of a variety ofpolyesters having two or more reactive hydroxyl groups, such as thepolyester polyols described above, which comprise the condensationreaction product of (a) a cycloaliphatic polyol and (b) a cyclicpolycarboxylic acid or anhydride.

When used to form the first urethane compound, the polyester polyoltypically has an Mn ranging from 300 to 3000, such as from 350 to 2500,or from 400 to 2200; also the hydroxyl value of the polyester polyolused here is typically greater than 90, such as from 100 to 180, or from110 to 170. The Tg values for the polyester polyol used to make thefirst urethane are as described above.

The monoisocyanate used in the formation of the first urethane compoundcan be any of a variety of isocyanate compounds that are monofunctionalwith regard to the NCO group. Nonlimiting examples of monoisocyanatesinclude cyclohexyl isocyanate, phenyl isocyanate, butyl isocyanate andmixtures thereof, with cyclohexyl and phenyl isocyanates beingparticularly suitable. The first compound can be prepared by generalNCO/OH reaction techniques well known in the art, so long as the ratioof the polyol and monoisocyanate and the reaction conditions are suchthat the resulting reaction product comprises at least one, such as two,reactive urethane NH groups per molecule. The molar ratio of thepolyester polyol to the monoisocyanate typically ranges from 1:1.7 to2.0, such as from 1:1.75 to 2.0, or from 1:1.8 to 2.0.

The first urethane compound can be prepared as follows. Typically, thepolyester polyol is dissolved in an appropriate aromatic solvent, forexample xylene or toluene, with a tin catalyst, for example dibutyl tindilaurate or dibutyl tin diacetate. The mixture is then preheated toapproximately 55° C. and the monoisocyanate is added dropwise. Theaddition rate is typically adjusted so that the reaction temperature isless than 90° C. The reaction is complete when all the isocyanatefunctionality is consumed.

The second urethane compound suitable for use as the modifying componentcomprises the reaction product of (a) a polyisocyanate and (b) amonohydric capping agent. Nonlimiting examples of polyisocyanatesinclude aliphatic polyisocyanates, such as aliphatic diisocyanates, forexample, 1,4-tetramethylene diisocyanate and 1,6-hexamethylenediisocyanate; cycloaliphatic polyisocyanates, for example,1,4-cyclohexyl diisocyanate, isophorone diisocyanate, and a,a-xylylenediisocyanate; and aromatic polyisocyanates, for example,4,4′-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, andtoluene diisocyanate. These and other suitable polyisocyanates aredescribed in more detail in U.S. Pat. No. 4,046,729, at column 5, line26 to column 6, line 28, incorporated herein by reference. Higherpolyisocyanates, for example isophorone diisocyanate trimer andhexamethylene diisocyanate trimer are also useful and, typically, aremore suitable. Mixtures of polyisocyanates can also be used.

The monohydric capping agent can comprise any of a wide variety ofmonohydroxyl functional materials. Typically, the monohydric cappingagent comprises one or more lower aliphatic alcohols, for example cyclicand acyclic alcohols having 1 to 6 carbon atoms in the alkyl groupand/or aromatic alcohols. Nonlimiting examples include methanol,ethanol, propanol, butanol, hexanol, cyclohexanol and phenol. In oneembodiment, the monohydric capping agent is methanol, cyclohexanol,phenol or mixtures thereof; cyclohexanol is especially suitable.

The second urethane compound can be prepared in much the same way as thefirst, but with the polyisocyanate being dissolved in the aromaticsolvent and the monohydric capping agent being added dropwise. Also theratio of NCO equivalents of the polyisocyanate to OH equivalents of themonohydric capping agent typically ranges from 0.70 to 1.0:1, such asfrom 0.75 to 1.0:1, or from 0.8 to 1.0:1.

Still more modifying components within the present invention includethose having the following structure (IV):

wherein X₁ is aromatic or cycloaliphatic; R₉, R₁₀, and R₁₁ can be thesame or different and each independently represents H, (cyclo)alkylgroups having from 1 to 12 carbon atoms, aryl, alkylaryl, or an activehydrogen-containing group that is reactive with the aminoplast, providedthat at least one of R₉, R₁₀, and R₁₁ is such an activehydrogen-containing group. Alkyl, aryl and alkylaryl are all describedabove. Especially suitable X groups include cyclohexyl, phenyl,naphthyl, anthracyl, pyrene, benzofuranyl, and the like. “Activehydrogen containing group” refers generally to a group that has one ormore active hydrogens, such as those provided by hydroxyl, amide, amine,carboxylic acid, carbamate, urea, and thiol groups.

In one embodiment, the modifying component comprises at least onecompound having structure (IV) wherein at least one of R⁹, R¹⁰, and R¹¹represents a group comprising at least one hydroxyl group. Examples ofactive hydrogen-containing compounds within structure (IV) includebenzyl alcohol and substituted benzyl alcohols, such as 3-phenoxybenzylalcohol and 4-methoxybenzyl alcohol; phenethyl alcohol; benzopinacol;N-benzylformamide; benzyl lactate; benzyl mandelate; benzyl mercaptan;N-benzylmethamine; 3-furanmethanol; furfuryl alcohol; pyridylcarbinols,such as 2-pyridylcarbinol, and 3-pyridylcarbinol; 1-pyrenemethanol;9-anthrancenemethanol; 9-fluorenemethanol; 9-hydroxyfluorene;9-hydroxyxanthene; 9-phenylxanthen-9-ol; 4-stilbenemethanol; andtriphenylmethanol.

Another modifying component useful in the present invention comprisescompounds having the following structure (V):

or dimer derivatives thereof as discussed below, where R₁₂ and R₁₃ arethe same or different and each independently represents an aryl grouphaving 4 to 20 carbons or an alkyl group having 1 to 12 carbon atoms. Inone embodiment of the present invention, one or both of R₁₂ and R₁₃ arearyl groups, for example, phenyl, naphthyl, methoxy phenyl, anddimethylaminophenyl groups. The aryl groups can also contain one or moreheteroatoms, such as O, N, and S, either internal or external to anaromatic ring of the aryl group. The heteroatoms external to the ringmay be attached directly to the ring or indirectly through one or morecarbon atoms. One or more heteroatoms may be present in each suchsubstituent and one or more substituents may be attached to an aromaticring of the aryl group. The heteroatom-containing substituent group(s)may be attached to an aromatic ring of the aryl group in any position orcombination of positions on the ring. Suitable heteroatomic substituentgroups include but are not limited to amines, ethers, esters, ketones,amides, halides, sulfonamides, nitro and carboxylic acid groups.Heteroatoms internal to the aromatic ring of this structure may bepresent in any position or combination of positions. Examples caninclude but are not limited to furans, pyridines, thiophenes, triazines,imidazoles, oxazoles, thiazoles, pyrazoles and triazoles. Nonlimitingexamples of such compounds having Structure V include anisoin, pyridoin,furoin, and bufyroin.

Compounds having the general structure (V) above are known to formdimeric derivatives, particularly when R₁₂ and R₁₃ are alkyl:

Such dimer derivatives can have the structure (VI) above where R₁₂ andR₁₃ are as described above for the structure (V).

Yet another modifying component useful in the present invention is acompound that is different from any of the others described above, andis characterized as containing at least one reactive hydrogen and ashaving a melting point of at least 60° C. The melting point of acompound can be determined by using a standard capillary melting pointapparatus or by thermal analysis (ASTM E974-95). Generally, the meltingpoint of this powder forming compound will be less than 250° C., usuallyless than 220° C., and typically less than 200° C., and will generallybe at least 60° C., usually at least 80° C., and typically at least 90°C. or 100° C. The melting point can range between any combination ofthese values inclusive of the recited values. Nonlimiting examples ofsuch compounds suitable for use as modifying components includemono-alcohols such as borneol, norborneol, isoborneol,1-adamantanemethanol, 1-adamantanol, 2-methyl-2-adamantanol and5-norbornen-2-ol; secondary amides, such as aliphatic cyclic amides suchas 1-methylhydantoin, 2,4-thiazolidinedione, 2-azacyclotridecanone,3,4,5,6,7,8-hexahydro-2(1H)-quinoline,4-azatricyclo(4.3.1.1(3,8))undecan-5-one and 4-methoxy-3-pyrrolin-2-one;aliphatic open chain amides, such as N-(1-adamantyl)acetamide) andN-tert-butylacrylamide; aromatic (poly)cyclic amides, including lactams,such as 1-acetamidopyrene, 2-acetamide-3-nitro-9-fluorenone,2-acetoamide-7-fluorfluorene, 2-acetamidofluorene,4-acetamido-9-fluorenone, naphthol AS acetate,1-phenyl-3-pyrazolidinone,2,3-dimethyl-1-(4-methylphenyl)-3-pyrazolin-5-one,3,4-dimethyl-1-phenyl-3-pyrazolin-5-one,3-(4-ethoxyphenyl)-1-(2-nitrophenyl)-hydantoin, 4-acetamidoantipyrine,and 4-acetamidobenzaldehyde; aromatic open chain amides, such as3-acetamidocoumarin and p-acetophenetidide; and mono-urethanes such asthose obtained by reacting high melting point mono-alcohols (such asthose described immediately above) with suitable mono-isocyanates.

In a specific embodiment, the compound having a melting point ≧60° C. isa monofunctional sulfonamide with only one active hydrogen. It will beappreciated that such sulfonamides generally have the structure (VII):R₁₄SO₂NHR₁₅   (VII)wherein R₁₄ can be virtually any unreactive organic moiety. Examplesinclude H, (cyclo)alkyl having from 1 to 12 carbon atoms, aryl, alkaryl,aralkyl, alkoxy, or aryloxy, all of which can be substituted orunsubstituted and R₁₅ is a (cyclo)alkyl group having from 1 to 12 carbonatoms, aryl, alkaryl, aralkyl, alkoxy carbonyl, alkyl carbonyl, or anaryl carbonyl. Substituents R₁₄ and R₁₅ can also be intramolecularlyconnected. Specific examples of compounds within structure (VII) includeN-alkyl-p-toluene sulfonamide, and saccharine.

Additional modifying compounds according to the present invention arecarboxylic acid-containing compounds. A “carboxylic acid-containingcompound” refers to any compound that has at least one carboxylic acidfunctional group. A number of carboxylic acids can be used according tothe present invention, provided they are of the appropriate acidity.Generally, carboxylic acids having a pKa of >3, such as >4, aresuitable. “pKa” values reported herein refer to pKa as measured indeionized water at 25° C. “pKa” will be understood as a means forexpressing the strength of acids; the weaker the acid, the larger thepKa. If the pKa is below about 3, the acid will catalyze theself-condensation of the aminoplast resin; this will result in a gelledrather than an ungelled reaction product. Similarly, the use of apolycarboxylic acid alone can result in a gelled product. Thus, thecarboxylic acid-containing compound is most suitably a monofunctionalacid, or a mixture of monofunctional and polyfunctional acids. If such amixture is used, the polyfunctional acid should typically comprise ≦20percent of the mixture. Aromatic carboxylic acids, such as benzoic acidand its derivatives are particularly suitable; derivatives of benzoicacid include those materials having substituents on the phenyl ring ofthe benzoic acid molecule; examples include toluic acids, anisic acid,and 4-tert-butyl benzoic acid. Aromatic group-containing alkylcarboxylic acids such as cinnamic acid and phenyl acetic acid and itsderivatives are also suitable; derivatives of phenyl acetic acid includethose compounds wherein the phenyl ring of the acid is substituted.Other suitable monofunctional carboxylic acids include, but are notlimited to, hexahydrobenzoic acid, diphenyl acetic acid and those knownto one skilled in the art. Polycarboxylic acids suitable for use withone or more monofunctional carboxylic acids include phthalic acid,terephthalic acid, and trimellitic acid.

Particularly suitable modified aminoplasts are those prepared from thereaction between aminotriazine compounds having one or less nonalkylatedNH bond per triazine ring and a monohydroxy aromatic compound, forexample a monohydroxy phenol derivative.

The modified aminoplasts of the present invention can be prepared bycombining the aminoplast and modifying compound in a suitably equippedreaction vessel, typically with a suitable solvent and an appropriatestrong acid as catalyst. Any suitable solvent can be used; aromaticsolvents are particularly suitable, including but not limited to xylene,toluene, and mixtures thereof. Nonlimiting examples of strong acidssuitable for use as catalysts include, but are not limited to, p-toluenesulfonic acid and dodecyl benzene sulfonic acid. Normal condensationtechniques well known in the art can be used to combine the reactants.Generally, the reaction admixture is heated to a temperature rangingfrom 90° C. to 135° C., such as from 100° C. to 125° C., and held atthat temperature for a period sufficient to obtain an ungelled product.

In the preparation of the modified aminoplasts, the reactants arecombined in a molar ratio such that the aminoplast compound is inexcess. The reaction between aminoplast and modifying component isterminated when the end point is detected by infrared spectroscopy. Theappropriate end point will differ depending on the modifying component.For urethanes, for example, the reaction is monitored by infraredspectroscopy for the disappearance of urethane NH functionality relativeto an internal standard (such as the urethane carbonyl signal, whichwill remain unchanged during the reaction). For other modifyingcomponents, the end point can be determined based on the disappearanceof the OH signal. For example, the molar ratio of the aminoplast to mostof the modifying components described above can range from 0.5 to 5.0:1,such as from 1.8 to 4.0:1, or from 1.9 to 3.6:1. For the carboxylic acidembodiment, there is an excess of carboxylic acid as compared toaminoplast. For example, the molar ratio of carboxylic acid-containingcomponent to aminoplast can be greater than 1.5:1. With regard to theaminoplast compound, the theoretical molecular weight of the monomericaminoplast compound (that is, where the DP equals 1) is used tocalculate the “molar ratio”. Using the appropriate ratio, and carryingthe reaction to completion, ensures a stable-modified aminoplast that isessentially free of active hydrogen-containing functionality. Thereaction is monitored for the disappearance of activehydrogen-containing functionality relative to an internal standard viainfrared spectroscopy (i.e., a hydroxyl signal is compared to the signalof a structure that will remain essentially unchanged as the reactionproceeds to completion, for example, the C—H stretch signal).

The modified aminoplasts typically have a Tg of at least −10° C., suchas at least 15° C., or at least 20° C., or 25° C. Also, the Tg istypically less than 150° C., such as less than 100° C., or less than 80°C. The Tg of the modified aminoplast can range between any combinationof these values, inclusive of the recited values. If the Tg is lowerthan about 20° C., it may not be in a form easily added to a powdercoating; in such instances, the product can be frozen to facilitate itsaddition to the coating formulation.

The aminoplasts used in the present additive can optionally be mixed orreacted with one or more functional siloxanes. Formulations includingsuch siloxane have been surprisingly discovered to impart even greatersilica dispersing ability to the aminoplast. A “functional siloxane”within the invention includes any alkyl-substituted polysiloxane havingas a substituent at least one active hydrogen-containing group, which isalso reactive with the aminoplast. The siloxanes used in the presentinvention can generally be represented by the structure (VIII):

wherein R₁₆, R₁₇, R₁₈, R₁₉, R₂₀, R₂₁, and R₂₃ can be the same ordifferent and can be a monovalent hydrocarbon group of 1 to 10 carbonatoms; R₂₂, R₂₄, and R₂₅ can be the same or different and can be adivalent hydrocarbon group of 1 to 24 carbon atoms; and Z₁, Z₂, and Z₃can be the same or different and can be H, OH, COOH, NH₂, NHR₂₆, CONH₂,CONHR₂₆, or NHCOOR₂₆ or any active hydrogen group reactive withaminoplasts where R₂₆ is a monovalent hydrocarbon group. The “n” and the“m” in the structure each indicate the number of their respectiverepeating units in the siloxane, and can be 0 to 12.

By “divalent hydrocarbon group” is meant an organic group containingcarbon and hydrogen. The hydrocarbon groups may be aliphatic oraromatic, and may contain from 1 to 24 (in the case of aromatic from 3to 24) carbon atoms. A “divalent hydrocarbon group” can also be aheteroatomic hydrocarbon group, that is, one or more of the carbonmolecules in the groups can be substituted with heteroatoms, typicallyoxygen or nitrogen. Nonlimiting examples of such divalent hydrocarbongroups include alkyl, alkoxyl, aryl, alkylaryl, alkoxyalkyl oralkoxyaryl groups, which are all as defined above.

In one embodiment of the present invention, n is 1 and m is 0 to 3, oneor all of R₁₆-₂₁ are methyl, R₂₆ is an aliphatic ether or polyether, Z₂is an alcohol, R₂₂ and R₂₅ are methylenes, and Z₁ and Z₃ are hydrogen.

Functional siloxanes include, for example, 1,1,1,3,3,5,5heptamethyl-5-(hydroxyethoxypropyl)trisiloxane,1,1,3,3-tetramethyl-1,3-di(hydroxyethoxypropyl)trisiloxane, and[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propoxy]-propanol.MASIL SF-19, commercially available from BASF, is a particular example.

In the embodiments in which siloxane is also used, it can be mixed withor reacted with the aminoplast. If the aminoplast is an unmodifiedliquid aminoplast, the siloxane can be added directly to the aminoplast,and if the aminoplast is an unmodified solid aminoplast, the aminoplastcan be dissolved or dispersed in organic solvent and the siloxanesubsequently added. When a modified aminoplast is used, the siloxane canbe reacted with the modified aminoplast under the same conditions asdescribed for the reaction between the aminoplast and modifyingcomponent. Alternatively, the siloxane can be reacted with theaminoplast at the same time as the modifying component; siloxane cansimply be added to the reaction vessel with the other components. Ineither case, the result will be an aminoplast that has reacted with botha modifying component and a siloxane.

When functional siloxane is used, the molar ratio of functional siloxaneto aminoplast ranges between 0.5 and 3:1.0, such as between 0.5:1.0.

The present additives are formed by mixing the aminoplasts describedabove with colloidal silica. Because colloidal silica is in liquid form,the aminoplast, during formation of the present additives, should alsobe in liquid form. If using a liquid aminoplast, no additional stepsneed be taken. Similarly, preparation of the modified aminoplasts takesplace in a solvent, and such a solution/disposition can be admixeddirectly with the silica nanoparticles. If a solid aminoplast that isnot already contained in a solvent is used, it should first be dissolvedor dispersed in one or more organic solvents. Suitable organic solventsinclude, for example, methyl isobutyl ketone, methyl ethyl ketone,methanol, and isopropanol. Mixture of the colloidal silica with theaminoplast can be effected by simply adding the solvent dispersednano-silica to a solution of the aminoplast. The resulting product canthen be stripped of solvent, such as through application of vacuum orother standard methods, to yield a powder additive in which silicananoparticles are dispersed throughout the aminoplast. The powderadditive can then be added to a powder or liquid coating. Alternatively,the additive can be kept in liquid form and added to a liquid coating toachieve enhanced mar and/or scratch resistance.

Suitable colloidal silica is commercially available from Nissan asMT-ST, MEK-ST, and MIBK-ST and from Clariant as HIGHLINK OG. The MEK-STand MIBK-ST products are 30 percent silica dispersions, in which thesurface of the silica particles has been modified to render theparticles stable in a non-hydroxy solvent; these surface modified silicaproducts are particularly suitable in the present methods.

The silica particles are typically below one micron in average particlesize, such as below 800 nanometers (“nm”). Such particles often have anaverage particle size in the 12 to 15 nm range. The aminoplast should beused in an amount sufficient to disperse the silica in the resultingaminoplast/silica mixture. The silica remains substantially evenlydispersed throughout the mixture both when the mixture is kept in liquidform or put in solid form. Typically, the silica comprises between 10and 40 weight percent of the additive. The weight ratio of silica toaminoplast is generally between 0.3 and 2:3, such as 1:3.

The additives of the present invention can be incorporated into coatingcompositions. Any resin that forms a film can be used in the presentcoatings, absent compatibility problems. For example, resins suitablefor either powder or liquid coating compositions can be used.

A particularly suitable resin is one formed from the reaction of apolymer having at least one type of reactive functional group and acuring agent having functional groups reactive with the functional groupof the polymer. The polymers can be, for example, acrylic, polyester,polyether or polyurethane, and can contain functional groups such ashydroxyl, carboxylic acid, carbamate, isocyanate, epoxy, amide andcarboxylate functional groups.

The use in powder coatings of acrylic, polyester, polyether andpolyurethane polymers having hydroxyl functionality is known in the art.Monomers for the synthesis of such polymers are typically chosen so thatthe resulting polymers have a Tg greater than 50° C. Examples of suchpolymers are described in U.S. Pat. No. 5,646,228 at column 5, line 1 tocolumn 8, line 7, incorporated herein by reference.

Acrylic polymers and polyester polymers having carboxylic acidfunctionality are also suitable for powder coatings. Monomers for thesynthesis of acrylic polymers having carboxylic acid functionality aretypically chosen such that the resulting acrylic polymer has a Tggreater than 40° C., and for the synthesis of the polyester polymershaving carboxylic acid functionality such that the resulting polyesterpolymer has a Tg greater than 50° C. Examples of carboxylic acidgroup-containing acrylic polymers are described in U.S. Pat. No.5,214,101 at column 2, line 59 to column 3, line 23, incorporated hereinby reference. Examples of carboxylic acid group-containing polyesterpolymers are described in U.S. Pat. No. 4,801,680 at column 5, lines 38to 65, incorporated herein by reference.

The carboxylic acid group-containing acrylic polymers can furthercontain a second carboxylic acid group-containing material selected fromthe class of C₄ to C₂₀ aliphatic dicarboxylic acids, polymericpolyanhydrides, low molecular weight polyesters having an acidequivalent weight from about 150 to about 750, and mixtures thereof.This material is crystalline and can be a low molecular weightcrystalline carboxylic acid group-containing polyester.

Also useful in the present powder coating compositions are acrylic,polyester and polyurethane polymers containing carbamate functionalgroups. Examples are described in WO Publication No. 94/10213,incorporated herein by reference. Monomers for the synthesis of suchpolymers are typically chosen so that the resulting polymer has a Tggreater than about 40° C.

Suitable curing agents generally include blocked isocyanates,polyepoxides, polyacids, polyols, anhydrides, polyamines, aminoplastsand phenoplasts. The appropriate curing agent can be selected by oneskilled in the art depending on the polymer used. For example, blockedisocyanates are suitable curing agents for hydroxy and primary and/orsecondary amino group-containing materials. Examples of blockedisocyanates are those described in U.S. Pat. No. 4,988,793, column 3,lines 1 to 36, incorporated herein by reference. Polyepoxides suitablefor use as curing agents for COOH functional group-containing materialsare described in U.S. Pat. No. 4,681,811 at column 5, lines 33 to 58,incorporated herein by reference. Polyacids as curing agents for epoxyfunctional group-containing materials are described in U.S. Pat. No.4,681,811 at column 6, line 45 to column 9, line 54, incorporated hereinby reference. Polyols, materials having an average of two or morehydroxyl groups per molecule, can be used as curing agents for NCOfunctional group-containing materials and anhydrides, and are well knownin the art. Polyols for use in the present invention are typicallyselected such that the resultant material has a Tg greater than about50° C.

Anhydrides as curing agents for epoxy functional group-containingmaterials include, for example, trimellitic anhydride, benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride,tetrahydrophthalic anhydride, and the like as described in U.S. Pat. No.5,472,649 at column 4, lines 49-52, incorporated herein by reference.Aminoplasts as curing agents for hydroxy, COOH and carbamate functionalgroup-containing materials are well known in the art. Examples of suchcuring agents include aldehyde condensates of glycoluril, which givehigh melting crystalline products useful in powder coatings. While thealdehyde used is typically formaldehyde, other aldehydes such asacetaldehyde, crotonaldehyde, and benzaldehyde can be used.

Hybrid resin systems, in which coreactive resins are used without acuring agent, can also be used. An example is an epoxy/polyether hybridsystem.

The film-forming resin described above is generally present in thepowder coating compositions in an amount greater than about 50 weightpercent, such as greater than about 60 weight percent, and less than 90weight percent, with weight percent being based on the total weight ofthe composition. For example, the weight percent of resin can be between60 and 70 weight percent. When a curing agent is used, it is generallypresent in an amount of between about 10 and 40 weight percent; thisweight percent is also based on the total weight of the coatingcomposition.

The present additives can also be incorporated into film-forming resinsthat are liquid, that is, water-borne or solvent-borne systems. Suchsolvents include, for example, alcohols, ketones, aromatic hydrocarbons,glycol ethers, esters or mixtures thereof. Examples of polymers usefulin forming the resin in the liquid coatings of the present inventioninclude hydroxyl or carboxylic acid-containing acrylic copolymers,hydroxyl or carboxylic acid-containing polyester polymers, oligomers andisocyanate or hydroxyl-containing polyurethane polymers, and amine orisocyanate-containing polyureas. These polymers are further described inU.S. Pat. No. 5,939,491, column 7, line 7 to column 8, line 2; thispatent, as well as the patents referenced therein, are incorporated byreference herein. Curing agents for these resins are also described inthe '491 patent at column 6, line 6 to line 62. In solvent-basedcompositions, the solvent is generally present in amounts ranging from 5to 80 weight percent based on total weight of the composition, such as30 to 50 percent. Even higher weight percents of solvent can be presentin water-based compositions and those that comprise water/cosolventmixtures.

It will be appreciated that the present compositions are distinct fromcompositions known in the art that comprise a resin, an aminoplastcuring agent (modified or unmodified) and silica in any form; information of such prior art compositions, there is no teaching that theaminoplast and silica be mixed together before addition of or to theresin. As such, the aminoplast in these prior art compositions is notused in an amount sufficient to disperse the silica. That is, theconcentration of aminoplast in these mixtures, as well as theinteraction of the aminoplast with other film-forming components, doesnot allow for suitable silica dispersion. In contrast, the presentadditives are formed so as to predisperse the silica in an aminoplastbefore combination with a film-forming resin. In addition to providingdispersed silica to the composition, the present additives may alsoreact with the other formulation components, thereby influencing thefilm's surface properties. A curing agent, if the resin is one requiringa curing agent, should still typically be used in addition to thepresent additives. The inventors do not wish to be bound by this or anyother particular mechanism, however.

The additives of the invention are typically present in the coatingcompositions in an amount ranging from 0.1 to 20.0 weight percent, suchas from 3.0 to 12 weight percent, or from 4.5 to 1 1 weight percent,with weight percent based on total weight of the coating composition.While amounts of 20 weight percent or less are typically suitable,amounts even greater than 20 weight percent can also be used. Typically,the weight percent of silica nanoparticles in the coating compositionranges between about 1 and 5, such as between about 1 and 4, or betweenabout 2 and 4, with weight percent based upon the total weight of thecomposition. It will be appreciated that improvement in mar and scratchresistance will increase as the concentration of the present additiveincreases. The tests described in the Example section below can be usedby those skilled in the art to determine what weight percent or “load”of the present additive will give the desired level of protection. Uponcuring of the coating, some of the silica nanoparticles may migrate tothe surface region (i.e. the top quarter of the coating layer). In oneembodiment, the silica nanoparticles can be fairly evenly dispersed inthe cured coating; in another embodiment there is an increasedconcentration of silica nanoparticles in the surface region of the curedcoating as compared with the bulk region (i.e. the bottom three-quartersof the coating).

The load of present additive in the coating compositions can affect notonly the level of mar and/or scratch resistance but also the appearanceof the cured coating. Thus, load should be optimized by the user basedon the particular application, taking into account, for example, thelevel of acceptable haze, the level of desired mar and/or scratchresistance, the thickness of the coating and the like. Where appearanceis particularly relevant, such as in an automotive clear coat, arelatively low load can be used. For industrial one-coat systems wherehaze is not as relevant, or where other pigments are present, loadingsof up to about 20 percent or even higher can be used. One skilled in theart can optimize load to achieve the desired level of mar and/or scratchresistance without compromising the appearance or other mechanicalproperties of the cured coatings.

The powder coating compositions of the present invention may optionallycontain additional additives such as waxes for flow and wetting, flowcontrol agents, such as poly(2-ethylhexyl)acrylate, degassing additivessuch as benzoin and MicroWax C, adjuvant resin to modify and optimizecoating properties, antioxidants, ultraviolet (UV) light absorbers andcatalysts. Examples of useful antioxidants and UV light absorbersinclude those available commercially from Ciba-Geigy under thetrademarks IRGANOX and TINUVIN. These optional additives, when used, aretypically present in amounts up to 20 percent by weight, based on totalweight of the coating.

The liquid coating compositions of the present invention can similarlycontain optimal additives such as plasticizers, antioxidants, lightstabilizers, UV absorbers, thixotropic agents, anti-gassing agents,organic cosolvents, biocides, surfactants, flow control additives andcatalysts. Any such additives known in the art can be used, absentcompatibility problems.

Micron sized particles can also be added. The average particle size ofthese materials can range from 0.1 to 10 microns, such as from 0.1 to 7microns, or from 0.6 to 4.6 microns. Examples include diamond particles,such as diamond dust particles, and particles formed from carbidematerials; examples of carbide particles include but are not limited totitanium carbide, silicon carbide and boron carbide. Other particlesinclude but are not limited to silica; alumina; alumina silicate; silicaalumina; alkali aluminosilicate; borosilicate glass; nitrides includingboron nitride and silicon nitride; oxides including titanium dioxide andzinc oxide; quartz; nepheline syenite; zircon such as in the form ofzirconium oxide; buddeluyite; and eudialyte. Mixtures of any of theabove particles can be used, including different combinations of organicparticles, inorganic particles, or both. The silica can be in anysuitable form, such as crystalline, amorphous, or precipitated. Thealumina can be used in any of its forms, such as alpha, beta, gamma,delta, theta, tabular alumina, and the like and can be fused orcalcined, and if calcined, ground or unground.

The particles listed above are widely commercially available. Forexample, crystalline silica is available from Reade Advanced Materials;amorphous and precipitated silica from PPG Industries, Inc.;ZEEOSPHERES, silica alumina ceramic alloy particles, from 3MCorporation; silica alumina, such as G200, G400, G-600, from 3MCorporation; alkali alumina silicate, such as W-210, W-410, and W-610,from 3M Corporation; borosilicate glass, sold as SUNSPHERES, from MoSciCorporation; and quartz and nepheline syenite from Unimin, Inc. Otheralumina products are available from Micro Abrasives Corporation as WCA3,WCA3S, and WCA3TO, and from Alcoa as T64-20. Zircon, buddeluyite andeudialyte are commercially available from Aran Isles Corporation, andboron nitride is available from Carborundum Inc. as SHP-605 and HPP-325.It will be appreciated that many commercially available products areactually composites or alloys of one or more materials; such particlesare equally within the scope of the present invention.

Microparticles can be added in weight percentages of from 0.1 to 20,such as 0.5 to 15, 0.1 to 10, or 0.1 to 0.5, based on the total weightof the composition. Use of micron sized particles contributes to the marand/or scratch resistance of the coating, but can also affect appearancein the same manner as described above for the silica nanoparticles usedin the present additives. Thus, the determination as to the appropriateamount of microparticles will be made by the user based on such thingsas the application, the weight percent of silica nanoparticlesincorporated through the present additives, and the like.

The additives of the present invention can be added at any time duringthe formulation of the coating. For example, curable powder coatingcompositions of the present invention can be prepared by first dryblending the film-forming resin, the present additive, and any of theadditional additives described above in a blender, such as a Henschelblade blender. The blender is operated for a period of time sufficientto result in a homogenous dry blend of the materials. The blend is thenmelt blended in an extruder, such as a twin screw co-rotating extruder,operated within a temperature range sufficient to melt but not gel thecomponents. The melt blended curable powder coating composition istypically milled to an average particle size of from, for example, 15 to80 microns. Other methods known in the art can also be used.

Alternatively, the present powder compositions can be prepared byblending and extruding the ingredients as described above, but withoutthe present additives. The present additives can then be added as apost-additive to the formulation, such as through a second extrusionprocess, or by simply mixing the particles into the blended composition,such as by shaking them together in a closed container or using aHenschel mixer.

For liquid coatings, the present additives can be added whenever anaminoplast would normally be added to a composition. For example, thepresent additives can be added to the coating composition underagitation after the film-forming resin is added. The present additivescan also be added under agitation after the solvents.

The coating compositions of the invention can be applied to a variety ofsubstrates, for example automotive substrates such as fenders, hoods,doors and bumpers, and industrial substrates such as householdappliances, including washer and dryer panels and lids and refrigeratordoors and side panels, lighting fixtures, metal office furniture. Suchautomotive and industrial substrates can be metallic, for example,aluminum and steel substrates, and non-metallic, for example,thermoplastic or thermoset (i.e. “polymeric”) substrates. Other objectsmade from wood and medium density fiberboard can also be coated with thepresent compositions.

The powder coating compositions are most often applied by spraying, andin the case of a metal substrate, by electrostatic spraying, or by theuse of a fluidized bed. The powder coating can be applied in a singlesweep or in several passes to provide a film having a thickness aftercure of from about 1 to 10 mils (25 to 250 micrometers), usually about 2to 4 mils (50 to 100 micrometers). Other standard methods for coatingapplication can be employed such as brushing, dipping or flowing.

The liquid compositions of the invention can also be applied by anyconventional method such as brushing, dipping, flow coating, rollcoating, conventional and electrostatic spraying. Spray techniques aremost often used. Typically, film thickness for liquid coatings can rangebetween 0.1 and 5 mils, such as between 0.1 and 1 mil, or about 0.4mils.

Generally, after application of the coating composition, the coatedsubstrate is baked at a temperature sufficient to cure the coating.Metallic substrates with powder coatings are typically cured at atemperature ranging from 250° F. to 500° F. (121.1° C. to 260.0° C.) for1 to 60 minutes, or from 300° F. to 400° F. (148.9° C. to 204.4° C.) for15 to 30 minutes.

Several liquid formulations can be cured at ambient temperature, such asthose using a polyisocyanate or polyanhydride curing agent, or they canbe cured at elevated temperatures to hasten the cure. An example wouldbe forced air curing in a down draft booth at about 40° C. to 60° C.,which is common in the automotive refinish industry. The ambienttemperature curable compositions are usually prepared as a two (2)package system in which the curing agent is kept separate from thecomposition containing the reactive functional group. The packages arecombined shortly before application.

The thermally curable liquid compositions such as those using blockedisocyanate, aminoplast, phenoplast, polyepoxide or polyacid curing agentcan be prepared as a one-package system. These compositions are cured atelevated temperatures, typically for 1 to 30 minutes at about 250° F. toabout 450° F. (121° C. to 232° C.) with temperature primarily dependentupon the type of substrate used. Dwell time (i.e., time that the coatedsubstrate is exposed to elevated temperature for curing) is dependentupon the cure temperatures used as well as wet film thickness of theapplied coating composition. For example, coated automotive elastomericparts require a long dwell time at a lower cure temperature (e.g., 30minutes 250° F. (121° C.)), while coated aluminum beverage containersrequire a very short dwell time at a very high cure temperature (e.g., 1minute 375° F. (191° C.)).

The coating compositions of the invention are particularly useful asprimers and as color and/or clear coats in color-clear compositecoatings. The compositions of the invention in the pigmented form can beapplied directly to a substrate to form a color coat. The color coat maybe in the form of a primer for subsequent application of a top coat ormay be a colored top coat. Alternatively, the coating composition of theinvention can be unpigmented, in the form of a clearcoat for applicationover a color coat (either a primer coat or a colored topcoat). When usedas a primer coating, thicknesses of 0.4 to 4.0 mils are typical. Whenused as a color topcoat, coating thicknesses of about 0.5 to 4.0 milsare usual, and when used as a clearcoat, coating thicknesses of about1.5 to 4.0 mils are generally used.

Accordingly, the present invention is further directed to a substratecoated with one or more of the present compositions. The substrates andcompositions, and manner of applying the same, are as described above.

The present invention is further directed to a multi-layer compositecoating composition comprising a base coat deposited from a film-formingcomposition and a topcoat applied over at least a portion of the basecoat, where the topcoat is deposited from any of the coatingcompositions of the present invention. The base coat might have a curedfilm thickness between about 0.5 and 4 mils (12.5 and 100 micrometers)while the topcoat cured film thickness can be up to 10 mils (250micrometers). The base coat can be cured before application of thetopcoat, or the two coats can be cured together. In one example, thebase coat can be deposited from a pigmented film-forming composition,while the topcoat formed from the present compositions is substantiallytransparent. This is the color-plus-clear system discussed above,frequently used in automotive applications.

In yet another embodiment, the present invention is directed to a methodfor improving the mar and/or scratch resistance of a coated substratecomprising applying the present compositions to at least a portion ofthe substrate. Application can be by any means known in the art to thethicknesses described above.

The coatings formed according to the present invention have outstandingappearance properties and scratch and mar resistance properties ascompared to no particles being present. Gloss retention percentagesfollowing mar and/or scratch testing ranging from about 20 percent up tonear 90 percent are achieved, such as 25 percent or greater retention,60 percent or greater retention, or 80 percent or greater retention. Todetermine whether improved mar and/or scratch resistance is obtainedwith the additives of the present invention, two coating compositionscan be formulated, with the only difference being that one contains thepresent additives and one does not. The coatings can be tested for marand/or scratch resistance (i.e. “mar and/or scratch testing”) by meansstandardly known in the art, such as those described in the Examplesection below. The results for the additive-containing andnonadditive-containing compositions can be compared to determine whetherimproved resistance is obtained when the present additives are added.Even a small improvement in any of these tests constitutes animprovement according to the invention.

As used herein, unless otherwise specified, all numbers such as thoseexpressing values, ranges, amounts or percentages may be read as ifprefaced by the word “about”, even if the term does not expresslyappear. Also, any numerical range recited herein is intended to includeall sub-ranges subsumed therein. As used herein, the term “polymer”refers to oligomers and both homopolymers and copolymers and the prefix“poly” refers to two or more. Unless stated otherwise, as used herein,molecular weights are number average molecular weights for polymericmaterials indicated as “Mn” and obtained by gel permeationchromatography using a polystyrene standard in the art-recognizedmanner.

EXAMPLES

The following examples are intended to illustrate the invention, andshould not be construed as limiting the invention in any way.

For all of the Examples, unless otherwise noted, 20° gloss was measuredwith a Haze-gloss Reflectometer Model 4601 available from BYK-Gardner.

1, 2, and 9μ 3M abrasive paper mar resistance testing (“1, 2 or 9μPaper”) were performed using an Atlas AATCC Mar Tester, Model CM-5,available from Atlas Electrical Devices Company, Chicago, Ill. A 2″×2″piece of Abrasive Paper (281 Q WETORDRY Production Polishing PaperSheets from 3M) backed with a felt cloth was clamped to the acrylicfinger on the arm of the instrument, and a set of 10 double rubs was runon each panel. The panel was then washed with cool tap water and dried.In the tables below, scratch resistance is the percentage of the 20°gloss that was retained after the surface was scratched by the scratchtester or percent gloss retention. Scratch resistance was measured as:Scratch Resistance=(Scratched Gloss÷Original Gloss)×100.

Steel wool scratch resistance tests were also performed using the AtlasTester (“steel wool”) in the same manner as the mar tests only using a2″×2″ piece of #0 grade steel wool sheet backed with the felt cloth.

Values reported in the tables below for paper and steel wool tests arepercent gloss retention.

Example 1

A carbinol functional siloxane having Structure VIII was prepared byhydrosilylation. Specifically, 1.2 parts by weight of1-allyloxy-2-propanol in the presence of a catalytic amount ofchloroplatinic acid (10 ppm platinum as a solution of 7.5% by weight inisopropanol) and 0.004 parts by weight of magnesium silicate was warmedto 80° C. under inert atmosphere. One part by weight1,1,1,3,5,5,5-heptamethyltrisiloxane was added through an additionfunnel over 5 hours. The mixture was treated with 0.02 parts by weightof a 35% solution of aqueous hydrogen peroxide and stirred for two hoursat 80° C. Filtration yields[3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxanyl]propoxy]-propanol(CAS# [77623-99-5]) as a water white liquid.

Example 2

A mixture of 1 part by weight CYMEL 303((methoxymethyl)melamine-formaldehyde from Cytec Industries, Inc.), 0.75parts by weight 2,4-di-tert-butylphenol and 0.75 parts by weight xylenewas heated to 120° C. in the presence of 0.001 parts by weightp-toluenesulfonic acid under inert atmosphere. The reaction vessel wasfitted with a distillation head and distillate was collected at a headtemperature of 65° C. until there was no visible hydroxyl peak in theinfrared spectrum. To the reaction mixture, 0.45 parts by weight of thesiloxane prepared according to Example 1 was added and distillate wascollected until there was no visible hydroxyl peak in the infraredspectrum. The acid catalyst was neutralized with the addition of 0.0025parts by weight of sodium carbonate. The reaction mixture was cooled to80° C. and 3.1 parts by weight of Nissan MEK-ST (30% colloidal silica inmethyl ethyl ketone) were mixed in. Solvents were removed under reducedpressure to yield a solid resinous mixture, referred to as “Additive A”below.

Example 3

Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanic stirrer, a nitrogen inlet, and a separator wereplaced 955.0 parts by weight of hydrogenated Bisphenol-A, 308.0 parts byweight of hexahydrophthalic anhydride, 1.3 parts by weight of di-butyltin oxide, and 1.3 parts by weight of triisodecylphosphite. The mixturewas melted by heating and was further heated to 230° C. while the waterresulting from the reaction was removed through the separator. Thereaction was stopped when an acid value of two was achieved. Thepolyester had a hydroxyl number of 160 and Tg around 65° C.

Example 4

A mixture of 1 part by weight CYMEL 300((methoxymethyl)melamine-formaldehyde from Cytec Industries, Inc.), 0.36parts by weight of the polyester prepared according to Example 3, and0.55 parts by weight xylene were heated to 120° C. in the presence of0.001 parts by weight p-toluenesulfonic acid under inert atmosphere. Thereaction vessel was fitted with a distillation head and distillate wascollected at a head temperature of 65° C. until there was no visiblehydroxyl peak in the infrared spectrum. To the reaction mixture, 0.23parts by weight of the siloxane prepared according to Example 1 wasadded and distillate was collected until there was no visible hydroxylpeak in the infrared spectrum. The acid catalyst was neutralized withthe addition of 0.0024 parts by weight of sodium carbonate. The reactionmixture was cooled to 80° C. and 2.37 parts by weight of Nissan MEK-STwere mixed in. Solvents were removed under reduced pressure to yield asolid resinous mixture, referred to as “Additive B” below.

Example 5

Into a five-liter, four-necked reaction kettle equipped with athermometer, a mechanic stirrer, a nitrogen inlet, and means forremoving the by-product (methanol) were placed 1280.0 parts by weight ofCYMEL 303, 947.6 parts by weight of 2,4-di-tert-butylphenol, 900.0 partsby weight of xylene, and 1.00 part by weight of p-toluenesulfonic acid.The mixture was heated to 120° C. and the temperature was maintainedwhile the methanol by-product was removed from the system. The reactionprogress was monitored by measuring the IR spectra of the mixture andwas terminated when the end point was detected. The mixture wassubsequently cooled to 100° C.; 184.8 parts by weight of the siloxaneprepared as described in Example 1 and 135.5 parts by weight of xylenewere added. The mixture was reheated to 120° C. and the methanolby-product was further removed. The reaction progress was continuouslymonitored by measuring the IR spectra of the mixture and was terminatedwhen an end point was detected. The mixture was then cooled to 100° C.and 2.80 parts by weight of sodium carbonate were added. The mixture wasfurther stirred at 100° C. for one hour before being filtered through a25 micron filtration bag. Thereafter, half of the mixture wasconcentrated at a temperature of 100° C. to 130° C. in a vacuum of 3 to50 mm Hg to remove the xylene solvent. The product thus obtained was apale yellow solid with a softening temperature of around 67° C.,referred to as “Additive C” below. The rest of the filtrate was used asa starting material for the synthesis of Additive D, described inExample 6.

Example 6

Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanic stirrer, a nitrogen inlet, and means forremoving the solvent were placed 1519.0 parts by weight of the filtratefrom the reaction described in Example 5 and 758.1 parts by weight ofMEK-ST. The solvent was removed at a temperature of 70° C. to 115° C. ina vacuum of 3 to 50 mm Hg. The product thus obtained was a pale yellowsolid with a softening temperature of around 58° C., referred to belowas “Additive D”.

Example 7

Into a five-liter, four-necked reaction kettle equipped with athermometer, a mechanic stirrer, a nitrogen inlet, and means forremoving the by-product (methanol) were placed 1440.0 parts by weight ofCYMEL 303, 844.6 parts by weight of 2,4-di-tert-butylphenol, 1016.0parts by weight of xylene, and 1.00 part by weight of p-toluenesulfonicacid. The mixture was heated to 120° C. and the temperature wasmaintained while the methanol by-product was removed from the system.The reaction progress was continuously monitored by measuring the IRspectra of the mixture and was terminated when an end point wasdetected. The mixture was then cooled to 100° C. and 2.80 parts ofsodium carbonate were added. The mixture was further stirred at 100° C.for one hour, and then filtered through a 25 micron filtration bag. Intoa two-liter, four-necked reaction kettle equipped with a thermometer, amechanic stirrer, a nitrogen inlet, and means for removing the solventwere placed 1689.0 parts by weight of the filtrate from the previousstep and 844.5 parts by weight of MEK-ST. The solvent was removed at atemperature of 70° C. to 115° C. in a vacuum of 3 to 50 mm Hg. Theproduct thus obtained is a pale yellow solid with a softeningtemperature of around 70° C., and is referred to as “Additive E”.

Example 8

GMA acrylic clear coat compositions identified as Samples 1 to 4 inTable I were prepared using the components and amounts (in grams) shown,and processed in the following manner. The components were blended in aHenschel Blender for 60 to 90 seconds. The mixtures were then extrudedthrough a Werner & Pfleider co-rotating twin screw extruder at a 450 RPMscrew speed and an extrudate temperature of 100° C. to 125° C. Theextruded material was then ground to a particle size of 20 to 35 micronsusing an ACM Grinder (Air Classifying Mill from Micron Powder Systems,Summit, N.J.). Cold rolled steel test panels were coated with PPG BlackElectrocoat primer ED5051, fully cured, and were obtained from ACTLaboratories. The finished powders were electrostatically sprayed ontotest panels and evaluated for coatings properties as further indicatedin the table. TABLE 1 Sample Sample Sample Sample 1 2 3 4 AlmatexPD-9060¹ 403.9 403.9 403.9 403.9 DDDA² 88.8 88.8 88.8 88.8 Additive C³ —— — 55.0 Additive D⁴ — 31.0 71.0 Benzoin⁵ 1.9 1.9 1.9 1.9 Triphenyl TinHydroxide⁶ 5.0 5.0 5.0 5.0 Modaflow⁷ 5.4 5.4 5.4 5.4 Total 505.0 536.0576.0 560.0 % melamine — 4.7% 10.1% 9.8% % silica — 1.0% 2.2% — Initialgloss 83.3 81.5 78.8 85.4 9 μm paper (% retention) 14.2% 46.4% 60.9%24.2% 3 μm paper (% retention) 21.1% 73.9% 80.2% 32.9% 2 μm paper (%retention) 65.5% 89.8% 89.8% 45.4% Steel Wool (% retention) 12.6% 23.3%29.1% 21.4%¹40% GMA acrylic, commercialy available from Anderson Development.²Dodecanedioic acid, commercially available from DuPont Chemicals.³Siloxane functional melamine.⁴Siloxane functional melamine with 18% colloidal silica on solids.⁵Degasser.⁶Triphenyl tin hydroxide catalyst, commercially available from AtofinaChemicals.⁷An acrylic copolymer flow additive/anti-crater additive, commerciallyavailable from Solutia, Inc.

As can be seen from the results in Table 1, both of the samplescontaining the present additives (Samples 2 and 3) gave much bettermar/scratch resistance than Sample 1, which lacked the additive. Sample4, which contained the modified aminoplast but not silica, gave resultssimilar to Sample 1, demonstrating that it is the modifiedaminoplast/silica nanoparticle combination that gives mar and/or scratchresistance.

Example 9

Samples 5 and 6 were prepared and tested as described in Example 8, withthe components and amounts (in grams) shown in Table 2. TABLE 2 Sample 5Sample 6 Almatex PD-9060 403.9 403.9 DDDA 88.8 88.8 Additive A⁸ — 35.0Benzoin 1.9 1.9 Triphenyl Tin Hydroxide 5.0 5.0 Modaflow 5.4 5.4 Total505.0 540.0 % melamine — 4.5% % silica — 1.9% Initial gloss 83.3 83.1 9um paper (%) 14.2% 59.8% 3 um paper (%) 21.1% 81.5% 2 um paper (%) 65.5%89.9% Steel Wool 12.6% 39.1%⁸Benzoxazine-type melamine with 30% colloidal silica.

As can be seen, the sample containing the present additive (Sample 6)gave improved mar/scratch resistance as compared with the controllacking the present additive (Sample 5).

Example 10

Samples 7 and 8 were prepared and tested as described in Example 8, withthe components and amounts (in grams) shown in Table 3. TABLE 3 Sample 7Sample 8 Almatex PD-9060 403.9 403.9 DDDA 88.8 88.8 Additive B⁹ — 35.0Benzoin 1.9 1.9 Triphenyl Tin Hydroxide 5.0 5.0 Modaflow 5.4 5.4 Total505.0 540.0 % melamine — 4.5% % silica — 1.9% Initial gloss 83.3 82.5 9um paper (%) 14.2% 26.7% 3 um paper (%) 21.1% 51.2% 2 um paper (%) 65.5%83.9% Steel Wool 12.6% 43.5%⁹Melamine with polyester, 30% colloidal silica.

As can be seen, the sample containing the present additive (Sample 8)gave improved mar/scratch resistance as compared with the controllacking the present additive (Sample 7).

Example 11

Samples 9 and 10 were prepared and tested as described in Example 8,with the components and amounts (in grams) shown in Table 4. TABLE 4Sample 9 Sample 10 Almatex PD-9060 403.9 403.9 DDDA 88.8 88.8 Additive A— 35.0 Benzoin 1.9 1.9 Microgrit WCA 3¹⁰ 1.5 1.5 Triphenyl Tin Hydroxide5.0 5.0 Modaflow 5.4 5.4 Total 506.5 541.5 % melamine — 4.5% % silica —1.9% Initial gloss 83 82.7 9 um paper (%) 38.1% 75.7% 3 um paper (%)61.7% 89.8% 2 um paper (%) 91.0% 93.8% Steel Wool 81.6% 78.4%¹⁰Calcined alumina, median particle size 2.85-3.71μ, commerciallyavailable from Micro Abrasive Corporation.

Sample 10, comprising both the present additive and micro-particulatealumina, performed better overall than Sample 9, comprising the aluminaalone.

Example 12

Samples 11 and 12 were prepared and tested as described in Example 8,with the components and amounts (in grams) shown in Table 5. TABLE 5Sample 11 Sample 12 Almatex PD-9060 403.9 403.9 DDDA 88.8 88.8 AdditiveE — 70.0 Benzoin 1.9 1.9 Triphenyl Tin Hydroxide 5.0 5.0 Modaflow 5.45.4 Total 505.0 575.0 % melamine — 10.0% % silica — 2.2% Initial gloss83.3 83.2 9 um paper (%) 14.2% 42.7% 3 um paper (%) 21.1% 70.2% 2 umpaper (%) 65.5% 91.6% Steel Wool 12.6% 67.5%

Again, Sample 12 containing the present additive had much better mar andscratch resistance as compared with the control Sample 11, which lackedthe present additive.

Example 13

A mixture of 587 parts by weight CYMEL 303, 472 parts by weight of thesiloxane prepared according to Example 1 and 353 parts by weightSOLVESSO 100 (aromatic solvent, obtained from Exxon) was heated to 120°C. in the presence of 0.05 parts by weight p-toluenesulfonic acid underan inert atmosphere. The reaction vessel was fitted with a distillationhead and distillate was collected at a head temperature of 65° C. untilthere was no visible hydroxyl peak in the infrared spectrum. The acidcatalyst was neutralized with the addition of 1.5 parts by weight ofsodium carbonate. The reaction mixture was cooled to 80° C., and 1516parts by weight of Nissan MEK-ST (30% colloidal silica in methyl ethylketone) were mixed in. Solvents from the reaction mixture were removedby distillation as the reaction mixture was warmed from 80° C. to 120°C. After the distillation, resin solids were 79 percent; the resultingresin solution is referred to as “Additive F” below.

Example 14

Liquid clearcoat formulations were prepared by using the components andparts by weight (grams) shown in Table 6 below; for the formulations,each component was mixed sequentially with agitation.

It will be appreciated that Sample 13 contained unmodified liquidmelamine, Sample 14 the same unmodified liquid melamine and silica, andSample 15 the additive of the present invention made from the samemelamine and silica. The three samples were applied over blackelectrocoated steel panels. The panels used were cold rolled steelpanels (4 inches×12 inches (10.16 cm by 30.48 cm)). The steel panelswere coated with ED5051 electrocoat, available from PPG Industries, Inc.These test panels are available as APR₂₈₂₁₅ from ACT Laboratories, Inc.of Hillsdale, Mich. The clear coating compositions of Samples 13 to 15were each applied to these test panels using an 8-Path Wet FilmApplicator #14 available from Paul N. Gardner Company, Inc. to a targetdry film thickness (“DFT”) of about 1.5 mils (about 38 micrometers). Allcoatings were allowed to air flash at ambient temperature about 10minutes. Panels prepared from each coating were baked horizontally for30 minutes at 285° F. (141° C.) to cure the coating. TABLE 6 Sample 13Sample 14 Sample 15 Methyl n-amyl ketone 40.0 15.4 40.0 Acrylic resin¹¹102.4 102.4 102.4 Melamine¹² 35.0 35.0 — Poly-butyl acrylate¹³ 0.5 0.50.5 Dodecyl benzene sulphonic acid¹⁴ 1.4 1.4 1.4 Colloidal silica¹⁵ —50.1 — Additive F — — 65.69 Initial gloss 87 87 83 9μ paper 57 72 77 %gloss retention 66 83 93¹¹(14.5% n-butyl methacrylate 14.9% n-butyl acrylate, 20.4% hydroxyethylmethacrylate, 27.6% isobornylmethacrylate, 22.6% hydroxypropylmethacrylate) 63.4% solids in propylene glycol monomethyl ether andSOLVESSO Aromatic 100 (Exxon).¹²CYMEL 303, available from Cytec Industries, Inc.¹³A flow control agent having a weight average molecular weight of about6700 and an Mn of about 2600 made in xylene at 62.5% solids, availablefrom DuPont.¹⁴Solution of 70% Dodecylbenzenesulphonic acid in n-propanol.¹⁵MEK-ST colloidal silica in methyl ethyl ketone, available from NissanChemical.

As can be seen in Table 6, the additive of the present invention, whenused in a liquid coating, gave improved mar/scratch resistance ascompared with controls (Samples 13 and 14).

Example 15

A mixture of 483 parts by weight of CYMEL 303, 155 parts by weight of2,4-di-t-butylphenol, 138 parts by weight of saccharin and 254 parts byweight of xylene was heated to 120° C. in the presence of 0.31 parts byweight of p-toluenesulfonic acid under inert atmosphere. The reactionvessel was fitted with a distillation head and distillate was collectedat a head temperature of 65° C. until there was no visible hydroxyl peakin the infrared spectrum. To the reaction mixture, 209 parts by weightof the siloxane prepared according to Example 1 was added and distillatewas collected until there was no visible hydroxyl peak in the infraredspectrum. The reaction mixture was cooled to 80° C. and 1408 parts byweight of Nissan MEK-ST (30% colloidal silica in methyl ethyl ketone)were mixed in. Solvents were removed under reduced pressure to yield asolid resinous mixture, referred to as “Additive G” below.

Example 16

A mixture of 483 parts by weight of CYMEL 303, 276 parts by weight ofsaccharin and 310 parts by weight of xylene was heated to 120° C. in thepresence of 0.38 parts by weight of p-toluenesulfonic acid under inertatmosphere. The reaction vessel was fitted with a distillation head anddistillate was collected at a head temperature of 65° C. until there wasno visible hydroxyl peak in the infrared spectrum. To the reactionmixture, 209 parts by weight of the siloxane prepared according toExample 1 was added and distillate was collected until there was novisible hydroxyl peak in the infrared spectrum. The reaction mixture wascooled to 80° C. and 1383 parts by weight of Nissan MEK-ST (30%colloidal silica in methyl ethyl ketone) were mixed in. Solvents wereremoved under reduced pressure to yield a solid resinous mixture,referred to as “Additive H” below.

Example 17

Samples 16 through 18 were prepared and tested as described in Example8, with the components and amounts (in grams) shown in Table 7. Asdemonstrated in Table 7, Samples 17 and 18 containing the presentadditive, gave much better results than the control, Sample 16, whichlacked the additive. TABLE 7 Sample 16 Sample 17 Sample 18 AlmatexPD-9060 403.9 403.9 403.9 DDDA 88.8 88.8 88.8 Additive G — 35.0 —Additive H — — 35.0 Benzoin 1.9 1.9 1.9 Triphenyl Tin Hydroxide 5.0 5.05.0 Modaflow 5.4 5.4 5.4 Total 505.0 540.0 540.0 % melamine — 4.5% 4.5%% silica — 1.9% 1.9% Initial gloss 83.3 84.5 85.1 9 um paper (%) 14.2%49.5% 37.5% 3 um paper (%) 21.1% 75.9% 58.5% 2 um paper (%) 65.5% 88.6%86.7% Steel Wool 12.6% 71.2% 55.5%

Example 18

Samples 19 through 21 were prepared and tested as described in Example8, with the components and amounts (in grams) shown in Table 8.

As demonstrated in Table 8, a higher concentration of the presentadditive (Sample 21) gave overall better results than a lowerconcentration (Sample 20), with both being markedly better than thecontrol (Sample 19), which lacked the present additive. TABLE 8 Sample19 Sample 20 Sample 21 Almatex PD-9060 403.9 403.9 403.9 DDDA 88.8 88.888.8 Additive D — 31.0 71.0 Benzoin 1.9 1.9 1.9 Triphenyl Tin Hydroxide5.0 5.0 5.0 Modaflow 5.4 5.4 5.4 Total 505.0 536.0 576.0 % melamine —4.7% 10.1% % silica — 1.0% 2.2% Initial gloss 83.3 81.5 78.8 9 μm paper(% retention) 14.2% 46.4% 60.9% 3 μm paper (% retention) 21.1% 73.9%80.2% 2 μm paper (% retention) 65.5% 89.8% 89.8% Steel Wool (%retention) 12.6% 23.3% 29.1%

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art the numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

1. An additive comprising a mixture of: a) an aminoplast; and b) silicaparticles having an average particle size below one micron dispersed inorganic solvent, wherein the aminoplast is present in an amountsufficient to disperse the silica in the resulting mixture, and whereinthe aminoplast is a modified aminoplast formed from the reactionbetween: i) the aminoplast; and ii) a modifying component.
 2. Theadditive of claim 1, wherein the aminoplast is liquid at 20° C. 3-4.(canceled)
 5. The additive of claim 1, wherein the aminoplast is amelamine derivative.
 6. The additive of claim 5, wherein the melaminederivative is an aminotriazine compound having one or less non-alkylatedNH bond per triazine ring.
 7. The additive of claim 6, wherein theaminotriazine compound is (methoxymethyl) aminotriazine.
 8. The additiveof claim 1, wherein the aminoplast is a glycoluril derivative.
 9. Theadditive of claim 8, wherein the glycoluril derivative is an alkoxylatedaldehyde condensate of glycoluril.
 10. The additive of claim 9, whereinthe glycoluril derivative is tetra-methoxymethyl glycoluril.
 11. Theadditive of claim 1, wherein the modifying component comprises amonohydroxy aromatic compound.
 12. The additive of claim 1, wherein themodifying component comprises an aliphatic polyhydric compound.
 13. Theadditive of claim 1, wherein the modifying component comprises acycloaliphatic polyhydric compound.
 14. The additive of claim 1, whereinthe modifying component comprises an aromatic polyhydric compound. 15.The additive of claim 1, wherein the modifying component comprises apolyester polyol formed from a cycloaliphatic polyol and a cyclicpolycarboxylic acid or anhydride.
 16. The additive of claim 1, whereinthe modifying component comprises a urethane.
 17. The additive of claim1, wherein the modifying component comprises a monofunctionalsulfonamide having only one active hydrogen.
 18. The additive of claim1, wherein the modifying component comprises a monofunctional carboxylicacid-containing compound.
 19. The additive of claim 1, wherein themodifying component comprises a compound having the structure IV:

wherein X₁ is an aromatic or cycloaliphatic group; R₉, R₁₀, and R₁₁ arethe same or different and are independently selected from the groupconsisting of H, alkyl groups having from 1 to 12 carbon atoms, aryl,alkylaryl, and an active hydrogen-containing group that is reactive withthe aminoplast, provided that at least one of R₉, R₁₀, and R₁₁ is anactive hydrogen-containing group.
 20. The additive of claim 1, whereinthe modifying component has the structure (VI):

where R₁₂ and R₁₃ are the same or different and are selected from thegroup consisting of an aryl group and an alkyl group having 1 to 12carbon atoms.
 21. The additive of claim 1, wherein the modifyingcomponent has the structure (V):

where R₁₂ and R₁₃ are the same or different and each independentlyrepresents an aryl group or an alkyl group having 1 to 12 carbon atoms.22-23. (canceled)
 24. The additive of claim 1, wherein the aminoplastand silica mixture further comprises c) a functional siloxane. 25-27.(canceled)
 28. The additive of claim 1, wherein the aminoplast is anaminotriazine compound having one or less nonalkylated NH bond pertriazine ring, and the modifying component is a monohydroxy aromaticcompound. 29-30. (canceled)
 31. A coating comprising the additive ofclaim
 1. 32-34. (canceled)
 35. A substrate coated with the coating ofclaim
 31. 36-49. (canceled)